1. Field of the Invention
This invention generally relates to the field of apparatus control systems and more specifically to the field of time based apparatus control systems.
2. Description of the Related Art
Automatic control of devices, especially household electrical devices, such as lights, fountains, irrigation systems and swimming pool pumps, frequently requires that the devices be activated or deactivated at times relative to the time of the sunrise and sunset at the location of the device. The time of sunrise and sunset at a particular location, however, is not constant throughout the year at points on the earth that are removed from the equator. Sunrise and sunset times vary throughout the year as a function of the latitude of the location. The nominal time of day of sunrise and sunset is also a function of the longitude of the location within the time zone of the location. The time of sunrise and sunset at a given location can be accurately calculated based upon the latitude and longitude of the location, but determination of a location's latitude and longitude are at least inconvenient and often beyond the desired effort of people who are responsible for the control of these devices. Devices that are automatically controlled to operate at times relative to sunrise and sunset typically have a manually set time of day clock and manually set “on” and “off” times. The person responsible for the control of the device is required to manually adjust the “start” and “stop” times for the device as the sunrise and sunset times vary throughout the year. This manual adjustment is inconvenient and can lead to waste and energy inefficiency if the manual adjustments are not made. This manual adjustment is frequently performed only occasionally and is sometimes forgotten, thereby resulting in deviations of the start and stop time for the devices that vary from the desired times relative to sunrise and sunset.
Some electrical device controllers control estimate sunrise and sunset based upon a specification of a geographic region or district of a country. Small countries such as Japan have small geographic regions such, as districts, that are smaller than common US geographic regions, such as states. These countries can use a specification of geographic region to estimate sunrise and sunset times. These districts have small deviations between the estimated and actual time of sunrise and sunset within the district, but larger regions have larger differences that are not acceptable for timing operations in relation to sunrise and sunset, such as turning lights on and off.